A US woman who shot and killed her husband and two adult children before taking her own life is thought to have committed the shocking crime as a result of being ostracised from the religion she was raised in.

Every time I tell a mate I’m doing a story on cryptocurrency, they invariably ask me the same two questions: should they invest their own hard-earned money, and which cryptocurrency will get them a Lamborghini/yacht/island quickest?

ASIO underestimating number of Aussies in Syria, expert says

Australia's secret intelligence agency may be underestimating the number of Aussies participating in the conflicts in Iraq and Syria by as much as 20 per cent, an academic has claimed.

Turkish security expert Kerim Balci says ASIO's figure that there are around 110 Australian nationals fighting on both sides of the war is underweight, and is likely to be closer to around 140, with slightly more than half supporting ISIL and al-Nusra.

He made the comments at a briefing in Melbourne, as the Herald Sun reports, citing various sources and emphasising the low cost – if not the ease – of getting across the Turkish border into Syria, which he says can be as small as $20.

His contentions paint a wide margin of error for ASIO; last month, agency boss Duncan Lewis had 110 on the ground, with around 49 casualties, though it's believed two more Australians have died in the weeks since he spoke publicly.

ASIO, which estimates around 200 people on home soil have pledged out-and-out support for ISIL, is standing by its figures; whether or not they are ballpark numbers, Mr Lewis expressed particular concern at the average age of recruits.

"The demographic is young. If I was talking to you a couple of years ago typically we would have been talking about people in their late twenties, early thirties," the spy chief told the ABC last month.

"If you asked me for a median without being precise I would say it's in the early twenties, but the trend is down and we do have at the bottom end of that spectrum some people of astonishingly young age."

Mr Balci says one way to combat ISIL , infamous for its slick online propaganda machine, is with a stronger digital presence.